Fire Emblem Heroes is set in a universe where there are some heroes in every world, and an evil empire is conquering several worlds to capture these heroes. You and your band of heroes has to go and rescue these worlds, but as the plot progresses, you will realise that your own world is in danger and you'll often have to return to base to defend it.

The first thing we noticed is that the game’s 80MB download size is deceptive. The moment we fired up Fire Emblem Heroes, we were asked to download 46MB of content and after the tutorial was over, we were asked to download another 319MB of content. Unlike the console iterations of Fire Emblem games, Fire Emblem Heroes lacks the signature cutscenes we’ve come to expect. That’s a trade-off for convenience as mobile games have a strict size limit imposed simply by the lack of free space on most people’s smartphones.

Combat is one of the most important aspects of Fire Emblem Heroes. It requires you to balance attack and defence, and you can't just expect to win by recklessly charging at enemies. If you're imagining a simple battle where your heroes just slug it out, you're in for a surprise. The map can play a decisive role in how battles progress. Sometimes your units can use walls or chasms as cover, while at other times these will just get in the way when you want to attack the enemy. There are different types of units, with three basic types being red, blue, and green. This is similar to the rock, paper, scissors mechanic, where each type of unit is strong against one type, and weak against the other. A lot of battle tactics involves ensuring that red heroes are attacking green enemies, and so on.

These battles are engrossing and we found ourselves placing our archer behind walls and using one of the units to boost others’ attack stats to ensure maximum kills. It’s actually a good idea to just keep all your units near each other in most of the initial maps. This way there’s always someone to bail your units out and single units don’t get stranded in a far corner of the map. It’s often best to let the enemies come to you so you can control certain aspects of battle, such as positioning strong range units near bridges or walls. These tactics are more important than how strong your units are. Even with level 7 and 8 units we were almost wiped out on the easiest difficulty setting when we got tactics wrong in Fire Emblem Heroes.

There are a bunch of other units types to keep track of too, such as archers, mages, flying units, and spies. Each of these have their own strengths and weaknesses and you'll have to find the right balance during battle. Nintendo's Fire Emblem Heroes also has a secondary battle mechanic, where heroes have an assist skill which allows them to give fellow units a boost. This could be something simple, like a healing power, or a boost in attacking stats.

Fire Emblem Heroes has a main quest and four other worlds that you can play. One of these worlds lets you meet special heroes that aren't there in the main storyline. The others let you do things such as train, and duel. It's an ad-free, free-to-play game, but you can only keep playing as long as you have orbs, or stamina. Stamina keeps regenerating with time, and you can have a maximum of 50 stamina points. You need to use these points to start quests or battles. There are a number of items you can collect to improve your heroes as well.

We haven’t yet spent much time exploring how to upgrade heroes, but we did try a couple of games on tougher difficulty levels and that made us want to. The difficulty level can be punishing at times. Thankfully during battles there is no time limit so you can take your time and strategise.

Unfortunately Fire Emblem Heroes, just like Super Mario Run, requires an always-on Internet connection. This means long loading times if your connection is slow. If the connection drops, you can play and finish a quest but it won't save progress until you're back online. That's a shame because we've found that if you're on the go, it's nearly impossible to play the game.

We've been playing Fire Emblem Heroes for a few hours now, and the overall impression is pretty positive. What are your thoughts on the game? Tell us via the comments. And in case you live in a region where the game isn't officially available yet, we've already talked about how you can start playing now. Our full review of the game will be up soon.

Nintendo's Fire Emblem Heroes is available as a free download via iTunes and Google Play.